Non-variant specific antibody responses to the C-terminal region of merozoite surface protein-1 of Plasmodium falciparum (PfMSP-119) in Iranians exposed to unstable malaria transmission

The PfMSP-119 was genotyped in 50 infected subjects with P. falciparum collected during 2006-2008. Four GST-PfMSP-119 variants (E/TSR/L, E/TSG/L, E/KNG/F and Q/KNG/L) were produced in Escherichia coli and naturally occurring IgG antibody to these proteins was evaluated in malaria patients' sera (n = 50) using ELISA. To determine the cross-reactivity of antibodies against each PfMSP-119 variant in P. falciparum-infected human sera, an antibody depletion assay was performed in eleven corresponding patients' sera.Sequence data of the PfMSP-119 revealed five variant forms in which the haplotypes Q/KNG/L and Q/KNG/F were predominant types and the second most frequent haplotype was E/KNG/F. In addition, the prevalence of IgG antibodies to all four PfMSP-119 variant forms was equal and high (84%) among the studied patients' sera. Immunodepletion results showed that in Iranian malaria patients, Q/KNG/L variant could induce not only cross-reactive antibody responses to other PfMSP-119 variants, but also could induce some specific antibodies that are not able to recognize the E/TSG/L or E/TSR/L variant forms.The present findings demonstrated the presence of non-variant specific antibodies to PfMSP-119 in Iranian falciparum malaria patients. This data suggests that polymorphism in PfMSP-119 is less important and one variant of this antigen, particularly Q/KNG/L, may be sufficient to be included in PfMSP-119-based vaccine.Plasmodium falciparum is a major global health problem and is responsible for most cases of severe malaria and over one million deaths annually [1]. Increasing the drug-resistant P. falciparum strains [2,3] and also insecticide resistant Anopheles mosquito in different malaria-endemic regions of the world emphasizes the need for new controlling tools and strategies such as vaccine to combat P. falciparum.Development of an effective vaccine against P. falciparum malaria has been a long-standing goal for malaria research and despite many decades of study, no eff